FaRe: a Mathematica package for tensor reduction of Feynman integrals

We present FaRe, a package for Mathematica that implements the decomposition of a generic tensor Feynman integral, with arbitrary loop number, into scalar integrals in higher dimension. In order for FaRe to work, the package FeynCalc is needed, so that the tensor structure of the different contributions is preserved and the obtained scalar integrals are grouped accordingly. FaRe can prove particularly useful when it is preferable to handle Feynman integrals with free Lorentz indices and tensor reduction of high-order integrals is needed. This can then be achieved with several powerful existing tools.Comment: Matches version to appear on the International Journal of Modern Physics

Neutrino parameters and the N2N_2-dominated scenario of leptogenesis

We briefly review the main aspects of leptogenesis, describing both the unflavoured and the flavoured versions of the $N_2$-dominated scenario. A study of the success rates of both classes of models has been carried out. We comment on these results and discuss corrective effects to this simplest scenario. Focusing on the flavoured case, we consider the conditions required by strong thermal leptogenesis, where the final asymmetry is fully independent of the initial conditions. Barring strong cancellations in the seesaw formula and in the flavoured decay parameters, we show that strong thermal leptogenesis favours a lightest neutrino mass m_1\gtrsim10\,\mbox{meV} for normal ordering (NO) and m_1\gtrsim 3\,\mbox{meV} for inverted ordering (IO). Finally, we briefly comment on the power of absolute neutrino mass scale experiments to either support or severely corner strong thermal leptogenesis.Comment: Contribution to the Proceedings of the NuPhys2013 Conference: Prospects in Neutrino Physics, 19-20 December 2013, IOP, Londo

Cosmological horizons

The recently unveiled deep-field images from the James Webb Space Telescope have renewed interest in what we can and cannot see of the universe. Answering these questions requires understanding the so-called "cosmological horizons" and the "Hubble sphere." Here, we review the topic of cosmological horizons in a form that university physics teachers can use in their lessons, using the latest data about the so-called standard "Lambda cold dark matter" (?CDM) model. Graphical representations are plotted in terms of both conformal and proper coordinates as an aid to understand the propagation of light in the expanding universe at various epochs

Supersymmetric SO(10)SO(10)-inspired leptogenesis and a new N2N_2-dominated scenario

We study the supersymmetric extension of $SO(10)$-inspired thermal leptogenesis showing the constraints on neutrino parameters and on the reheat temperature $T_{\rm RH}$ that derive from the condition of successful leptogenesis from next-to-lightest right handed (RH) neutrinos ($N_2$) decays and the more stringent ones when independence of the initial conditions (strong thermal leptogenesis) is superimposed. In the latter case, the increase of the lightest right-handed neutrino ($N_1$) decay parameters helps the wash-out of a pre-existing asymmetry and constraints relax compared to the non-supersymmetric case. We find significant changes especially in the case of large $\tan\beta$ values $(\gtrsim 15)$. In particular, for normal ordering, the atmospheric mixing angle can now be also maximal. The lightest (ordinary) neutrino mass is still constrained within the range $10 \lesssim m_1/{\rm meV} \lesssim 30$ (corresponding to $75\lesssim \sum_i m_i/{\rm meV} \lesssim 120$). Inverted ordering is still disfavoured, but an allowed region satisfying strong thermal leptogenesis opens up at large $\tan\beta$ values. We also study in detail the lower bound on $T_{\rm RH}$ finding $T_{\rm RH}\gtrsim 1 \times 10^{10}\,{\rm GeV}$ independently of the initial $N_2$ abundance. Finally, we propose a new $N_2$-dominated scenario where the $N_1$ mass is lower than the sphaleron freeze-out temperature. In this case there is no $N_1$ wash-out and we find $T_{\rm RH} \gtrsim 1\times 10^{9}\,{\rm GeV}$. These results indicate that $SO(10)$-inspired thermal leptogenesis can be made compatible with the upper bound from the gravitino problem, an important result in light of the role often played by supersymmetry in the quest of a realistic model of fermion masses.Comment: 35 pages, 10 figures; v3: matches JCAP versio

A consistent model for leptogenesis, dark matter and the IceCube signal

We discuss a left-right symmetric extension of the Standard Model in which the three additional right-handed neutrinos play a central role in explaining the baryon asymmetry of the Universe, the dark matter abundance and the ultra energetic signal detected by the IceCube experiment. The energy spectrum and neutrino flux measured by IceCube are ascribed to the decays of the lightest right-handed neutrino $N_1$, thus fixing its mass and lifetime, while the production of $N_1$ in the primordial thermal bath occurs via a freeze-in mechanism driven by the additional $SU(2)_R$ interactions. The constraints imposed by IceCube and the dark matter abundance allow nonetheless the heavier right-handed neutrinos to realize a standard type-I seesaw leptogenesis, with the $B-L$ asymmetry dominantly produced by the next-to-lightest neutrino $N_2$. Further consequences and predictions of the model are that: the $N_1$ production implies a specific power-law relation between the reheating temperature of the Universe and the vacuum expectation value of the $SU(2)_R$ triplet; leptogenesis imposes a lower bound on the reheating temperature of the Universe at 7\times10^9\,\mbox{GeV}. Additionally, the model requires a vanishing absolute neutrino mass scale $m_1\simeq0$.Comment: 19 pages, 4 figures. Constraints from cosmic-ray antiprotons and gamma rays added, with hadrophobic assignment of the matter multiplets to satisfy bounds. References added. Matches version published in JHE

Zooplankton - indicator of ecological status in Mediterranean ponds

Mediteranske lokve su plitka vodena tijela koja često presušuju. U prošlosti su bile bitan izvor vode, a danas su izložene različitim negativnim antropogenim utjecajima. Zooplanktonski organizmi značajno pridonose bioraznolikosti lokvi, a ujedno su relevantni pokazatelji ekološkog stanja. Ciljevi ovog rada bili su utvrditi: (i) brojnosti i raznolikost zooplanktona te dominantne vrste i njihovu ekološku ulogu; (ii) utjecaj okolišnih čimbenika i predacije na sastav zooplanktona te (iii) povezanost funkcionalnih obilježja zooplanktona i ekološkog stanja kao osnova prijedloga mjera upravljanja i očuvanja jadranskih lokvi. U deset lokvi determinirano je 57 zooplanktonskih vrsta, a kolnjaci su dominirali sa 40 vrsta. Rezultati ukazuju da je na sastav zooplanktona značajno utjecala kompleksnost habitusa makrofita te ribe kao vizualni predatori. Zooplankton lokvi sa sumberznim makrofitima, bez riba, obilježavala je veća brojnost i raznolikost, te vrlo dobro ekološko stanje s većim udjelom planktonskih rakova. U lokvama dobrog ekološkog stanja s dominacijom kolnjaka, bile su prisutne ribe te pokrovnost emerznim i flotantnim makrofitima. Mala brojnost i raznolikost zooplanktona obilježavala je lokve umjereno promijenjenog ekološkog stanja s malom pokrovnošću makrofitima. Antropogeni utjecaji na mediteranske lokve iziskuju sustavno upravljanje i očuvanje lokvi kako bi se umanjili negativni utjecaji i obnovile njihove ekološke funkcije te očuvala bioraznolikost.Mediterranean ponds are shallow water bodies and often temporary. In the past, they were important sources of water, and recently are exposed to various negative anthropogenic impacts. Zooplankton organisms contribute significantly to pond biodiversity and are relevant indicators of ecological status. The objectives of this study were to establish: (i) the abundance and diversity of zooplankton and the ecological role of dominant species; (ii) the influence of environmental factors and predation on zooplankton composition; and (iii) the correlation of zooplankton functional traits and ecological status as basis for the proposal of management and conservation of Adriatic ponds. Among 57 zooplankton species, rotifers dominated with 40 species. The results indicate the zooplankton composition was significantly influenced by complexity of the macrophytes and fish predation. Zooplankton in ponds with submerged macrophytes, without fish, were characterized by high abundance and diversity in very good ecological status and higher ratio of planktonic crustaceans. In ponds of good ecological status with dominance of rotifers, fish were present, and coverage of emergent and flotant macrophytes. The low abundance and diversity of zooplankton marked ponds of moderately altered ecological status with scarce macrophyte coverage. Anthropogenic impacts on Mediterranean ponds require systematic management and conservation to minimize adverse impacts and restore their ecological functions and preserve biodiversity

Evidence of a large scale positive rotation-metallicity correlation in the Galactic thick disk

This study is based on high quality astrometric and spectroscopic data from the most recent releases by Gaia and APOGEE. We select $58\,882$ thin and thick disk red giants, in the Galactocentric (cylindrical) distance range $5 < R < 13$~kpc and within $|z| < 3$~kpc, for which full chemo-kinematical information is available. Radial chemical gradients, $\partial \rm{[M/H]} / \partial \rm{R}$, and rotational velocity-metallicity correlations, $\partial V_\phi / \partial \rm{[M/H]}$, are re-derived firmly uncovering that the thick disk velocity-metallicity correlation maintains its positiveness over the $8$~kpc range explored. This observational result is important as it sets experimental constraints on recent theoretical studies on the formation and evolution of the Milky Way disk and on cosmological models of Galaxy formation.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical Societ

Strong thermal leptogenesis and the absolute neutrino mass scale

We show that successful strong thermal leptogenesis, where the final asymmetry is independent of the initial conditions and in particular a large pre-existing asymmetry is efficiently washed-out, favours values of the lightest neutrino mass $m_1 \gtrsim 10\,{\rm meV}$ for normal ordering (NO) and $m_1 \gtrsim 3\,{\rm meV}$ for inverted ordering (IO) for models with orthogonal matrix entries respecting $|\Omega_{ij}^2| \lesssim 2$. . We show analytically why lower values of $m_1$ require a high level of fine tuning in the seesaw formula and/or in the flavoured decay parameters (in the electronic for NO, in the muonic for IO). We also show how this constraint exists thanks to the measured values of the neutrino mixing angles and can be tighten by a future determination of the Dirac phase. Our analysis also allows to place more stringent constraint for a specific model or class of models, such as $SO(10)$-inspired models, and shows that some models cannot realise strong thermal leptogenesis for any value of $m_1$. A scatter plot analysis fully supports the analytical results. We also briefly discuss the interplay with absolute neutrino mass scale experiments concluding that they will be able in the coming years to either corner strong thermal leptogenesis or find positive signals pointing to a non-vanishing $m_1$. Since the constraint is much stronger for NO than for IO, it is very important that new data from planned neutrino oscillation experiments will be able to solve the ambiguity.Comment: 22 pages; 7 figures; v2: matches JCAP versio